Nitride semiconductors such as gallium nitride (GaN) and the like are watched as a semiconductor material constituting a blue light emitting device, and recently, are expected to be able to realize a green light emitting device, further, a red light emitting device, by doping indium (In) at high concentration to GaN. When the concentration of In is higher, however, fluctuation of the In composition and the piezoelectric field effect become remarkable, thus, a red light emitting device using a nitride semiconductor has not been realized under present circumstances.
On the other hand, paying attention to wide gap of a nitride semiconductor, a semiconductor prepared by using GaN as a doping base and doping a rare earth element such as europium (Eu) and praseodymium (Pr) is regarded as promising as a red light emitting device.
Under such situation, the present inventors have led the world and succeeded in realization of a red light emitting diode (LED) using Eu or Pr-doped GaN as an active layer.
Owing to realization of such a red light emitting diode, it becomes possible to integrate light-emitting diodes of three primary colors of light using nitride semiconductors on the same substrate, combining with a blue light emitting diode and a green light emitting diode developed previously. Therefore, application thereof to fields of a compact and high-resolution full color display, LED illumination having added light emission in the red region not contained in current white LED, and the like, is expected.